Elastomeric videodisc mold

ABSTRACT

A matrix is used to prepare a mold of an elastomeric material. A polymerizable compound is coated onto a flexible, thin substrate such as Mylar and is placed with compound side in intimate contact with the mold. The compound is cured and is bonded to the substrate. The cured combination is stripped from the mold and is given a metallic coating to improve reflectivity. A clear plastic coating may be applied to protect the metal surface.

This application is a continuation of application Ser. No. 905,837,filed May 15, 1978 now abandoned, a div. of Ser. No. 753,184 filed Dec.22, 1976, now U.S. Pat. No. 4,130,620, a div. of Ser. No. 406,686 filedOct. 15, 1973, now abandoned.

RELATED PATENT APPLICATIONS AND PATENTS

"Articulated Mirror" by James E. Elliott, Ser. No. 333,559, filed Feb.20, 1973 now U.S. Pat. No. 3,794,410, issued Feb. 26, 1974; "Video DiscMastering System" by John S. Winslow, Ser. No. 333,560, filed Feb. 20,1973 now abandoned and continued as Ser. No. 508,815, filed Sept. 29,1974, a C.I.P. of which issued as U.S. Pat. No. 4,225,873;"Video DiscPlayer" by James E. Elliott, Ser. No. 314,082, filed Dec. 11, 1972;"Viedo Disc Player" by James E. Elliott, Ser. No. 299,893, filed Oct.24, 1972 now U.S. Pat. No. 3,829,622, issued Aug. 13, 1974; "VideoRecording and Recording and Reproducing System" by Kent D. Broadbent,Ser. No. 299,892, filed Oct. 24, 1972; "Drop-Out Compensator" by WayneRay Dakin, Ser. No. 299,891, filed Oct. 24, 1972; "Video Record Disc andProcess for Making Same" by David P. Gregg, Ser. No. 735,007, filed Jan.27, 1969 now abandoned and continued as Ser. No. 571,259, filed Apr. 24,1975; "Duplicating Process for Video Disc Records" by Kent D. Broadbent,U.S. Pat. No. 3,658,954, Issued Apr. 25, 1972; "Video Signal TransducerHaving Servo Controlled Flexible Fiber Optic Track Centering" by DavidP. Gregg and Keith O. Johnson, U.S. Pat. No. 3,530,258, Issued Sept. 22,1970; "Photoelectric Transducer Head" by David P. Gregg, U.S. Pat. No.3,349,273, Issued Oct. 24, 1967; "Video Disc Playback Assembly" by KeithO. Johnson, U.S. Pat. No. 3,518,442, Issued June 30, 1970; "DuplicatingProcess for Video Disc Records" by Kent D. Broadbent, U.S. Pat. No.3,687,664, Issued Aug. 29, 1972; "Reading Head for Video Disc Player" byManfred H. Jarsen, Ser. No. 402,635, filed Oct. 1, 1973, and now U.S.Pat. No. 3,947,888; "Method of Creating a Replicating Matrix" by ManfredH. Jarsen, Ser. No. 402,636, filed Oct. 1, 1973, a divisional of whichissued as U.S. Pat. No. 4,141,731; "Fluid Cushion Turntable for VideoDisc Player", by Manfred H. Jarsen, Ser. No. 402,634, filed Oct. 1,1973.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to information handling systems and moreparticularly to a process for producing replicas from a master matrixand to the mold and replicas produced from the process.

2. Description of the Prior Art

Over the years, there has been a continuing attempt to achieve a lowcost, mass produced disc which contains video information that can beretrieved with an inexpensive home instrument for playback for aconventional television set.

Early attempts at providing video information have generally involvedthe use of video tape recorders of various sorts as well as photographictechniques. Still other approaches have attempted to utilizethermoplastic records or the surface alteration of a thin metallic film.

In the co-pending application of Manfred H. Jarsen, Ser. No. 402,636,filed Oct. 1, 1973, entitled "Method of Creating a Replicating Matrixand the Matrix Created Thereby", assigned to the assignee of the presentinvention, methods were taught which led from a master video recording,such as in the co-pending application of John S. Winslow, Ser. No.333,560, filed Feb. 20, 1973, now abandoned and continued as Ser. No.508,815, filed Sept. 24, 1974 and assigned to the assignee of thepresent invention, to a three-dimensional matrix from which replicas canbe created.

In the co-pending Jarsen application, supra, the present casting processwas disclosed for producing a replica on a disc which includes a Mylarpolyester film substrate and a polymer layer, into which is molded theinformation contained in the matrix.

According to the present invention, the casting process includes theproduction of a principal mold which can be used to produce submatriceswhich, in turn, would produce submolds. Both the molds and the submoldscan be used to "cast" replicas. In the preferred embodiment of theprocess, a Mylar substrate of thickness from 4-10 mils is uniformlycoated with a very thin (approximately 3-7 microns) layer of apolymerizable resin to which a catalyst has been added.

The resin is then brought into contact with the mold and subjected topressure to assure that the resin fills all of the depressions and/orcavities of the mold. The resin is then permitted to cure. The bondbetween the Mylar substrate and the resin is perfected. After curing,the Mylar and polymerized resin are a unitary structure and, as such,can be peeled from the mold. The same mold can then be used again in thecasting of subsequent replicas using substantially the same techniques.

The replica, thus cast, is then provided with a reflective, metal layer,for example, through a vapor deposition process. If desired, an outer,wear layer of clear plastic can be applied.

In the video disc systems described in the related patents andapplications, one systems approach permits the use of a thin, flexibledisc, such as is produced by the present method. Such a disc can be readon appropriate playback equipment as has been heretofore disclosed.

If, the exigencies of mas production are such that insufficient moldscan be derived from a single matrix, it is feasible, according to thepresent invention, to cast a number of polymer, replicas in the firstmold which can function as submatrices, as well.

An alternate replica can be made from an acrylic-polyester combination.The acrylic replicas when plated, can be distributed as such. Theacrylic replicas could also be utilized as a starting element in theseries of plating steps that ultimately result in a stamper for use inthe alternative, stamping process of producing replicas.

In yet other, alternative casting methods, replicas can be produced byfirst flowing the resin-catalyst mixture into the mold. The Mylarpolyester film substrate is applied later, and becomes bonded to thecured resin.

The replica is then "peeled" off the mold. In the preferred embodiment,the cast replica is then subjected to a metallizing step in which asuitably reflective metal such as aluminum is applied to the surface.Vapor deposition of aluminum has been found to be satisfactory. Thereflective coating enhances the optical contrast between the deformedareas representing information and the plane areas adjacent thereto. Anadditional coating of a clear plastic, wear layer can be applied toprotect the metal film from scratches or abrasions.

It is obvious that the present method could be modified to producereplicas in which the surface deformations are depressions rather thanelevated portions, should that type of replica better lend itself to theplayback equipment. Further, the requirements of the playback equipmentwould also determine the size and shape of the surface deformationswhich represent the video information.

For example, in the system being developed by the assignee, a readingtechnique is employed which utilizes light scattering and lightreflection to generate electrical signals of different significance. Insuch a system, the "bumps" or "depressions" serve to scatter rather thanreflect light applied from the player device. The surface betweenadjacent bumps or depressions, however, serves as a plane reflector, andreturns substantially all of the light to the player optical system.

In the alternative schemes, phase contrast optics are employed in whichcase it is desirable that reflecting planes be spaced apart by nλ/4(where λ is the wavelength of the playback radiation and "n" is an oddinteger) be employed so that light reflected from a one of the surfacesis constructively interfered with, and light from the other of thesurfaces is destructively interfered with.

Given an original matrix having such characteristics, the presentprocess is admirably suited to produce replicas utilizing the mold ofthe present invention, that is created from the matrix.

The novel features which are believed to be characteristic of theinvention, both as to organization and method of operation, togetherwith further objects and advantages thereof, will be better understoodfrom the following description considered in connection with theaccompanying drawings in which several of the preferred embodiments ofthe invention are illustrated by way of example. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration and description only and are not intended as a definitionof the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portion of the surface of a mold madein accordance with the present invention;

FIG. 2 is a side section view of the apparatus used to produce the moldof FIG. 1;

FIG. 3 is a side section view of the mold of FIG. 2 taken along line3--3 in the direction of the appended arrows prior to the casting of areplica;

FIG. 4 is a side section view of apparatus for providing a polymerizableresin and substrate combination;

FIG. 5 including FIGS. 5a and 5b are side section views of the mold ofFIG. 1 with a resin and substrate combination being applied inalternative processes;

FIG. 6 is a side section view of the mold during the casting step;

FIG. 7 is a side section view of the polymerized resin and substratebeing removed from the mold;

FIG. 8 is a side section view of a cast acrylic replica in the mold; and

FIG. 9 is a perspective view of a portion of a replica disc partlybroken away to show the metal and plastic protective coatings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, there is shown in perspective view a portion of a mold 10made according to the process of the present invention. As will benoted, the mold 10 has an upper surface 12 in which is formed aplurality of depressions 14 generally arranged in a concentric spiraltrack 16.

Although the individual depressions are arranged in a generally circularpattern, the track 16 is a discontinuous one, and includes a flatsurface area 18 between adjacent depressions 14. The peferred embodimentof the present invention contemplates an information track 16 arrangedin a spiral, but alternative embodiments contemplate informationarranged in circular tracks, not shown, as well.

It is to be further noted that while the preferred embodimentillustrated in FIG. 1 shows each track 16 to include depressions 14, itis equally feasible to supply protuberances or "bumps" in place of thedepressions 14. If the surface features provided in the playback replicaare intended to scatter radiation rather than reflect it, the choice ofone or the other is dictated primarily by considerations of fabricationof the mold 10, or the replica to be cast in the mold 10.

The process of producing the mold 10 can be explained in connection withFIG. 2. The starting material should be a matrix 20, such as isdisclosed in the copending Jarsen application. As taught in thatapplication, the matrix is a glass disc 22 on which the videoinformation is arranged as a series of photoresist "bumps" 24approximately 0.7 micron high and generally 1 micron in the radialdirection. The bumps are generally arranged in a concentric, spiraltrack with a spacing of approximately two microns between the centers ofadjacent tracks.

The matrix 20 may or may not have remaining on the surface, a very thinlayer of a low melting point opaque material 26 such as is disclosed inthe copending Winslow application. A thin bismuth film has been found tobe suitable for this purpose. If desirable, the bismuth film 26 may beremoved utilizing a suitable chemical solvent. Such a step is generallynot undertaken in that it may jeopardize the integrity of theinformation pattern.

To prepare the matrix 20 for the present process, a mold releasecompound (not shown) is spun on to the matrix 20 and permitted to dry,after which it is baked. In one satisfactory process, a commercialrelease, identified as Fitzgerald Polyvinyl Alcohol Mold Release, isdiluted with three parts of water to each part of mold release.

With a matrix 20 such as is disclosed by Jarsen supra, approximately 25cc. of mold release is diluted to a total quantity of 100 cc., filteredand then applied to the matrix 20. The mold release is dried in air forapproximately 10 minutes, and the matrix is then baked at a temperatureof 300° F. for approximately 30 minutes.

As seen in FIG. 2, apparatus is shown which is suitable for use in theproduction of the mold 10. A heater unit 30 has, placed on its uppersurface, a block of aluminum 32 which is a good thermal conductor. Theglass-based matrix 20 is secured to the aluminum plate 32 using a wax 34which acts as both an adhesive and a cushion.

Spacers 36 are provided to create a volume in which the mold 10 can bemade. In the preferred embodiment, first spacers 36, approximately 14mils high, are placed around the periphery of the matrix 20, and asecond spacer 38 approximately 7 mils in thickness is placed at thecenter of the matrix disc.

A glass plate 40 is coated with a primer compound 42 to which theelastomeric material comprising the mold will adhere. One such primermaterial is sold under the designation Primer SS4120 by the GeneralElectric Company. The primer coating 42 is permitted to air dry forapproximately 30 minutes.

In the preferred embodiment, the mold is made of a silicone rubberelastomer, such as is sold by the General Electric Company under thedesignation RTV 615A silicone rubber. In the process, being describedherein, it has been found that approximately 200 grams of the siliconerubber, with 20 grams of the proper catalyst for that compound, aresufficient to make a roughly 15 inch diameter mold that is approximately14 mils thick.

The mixture of silicone rubber and catalyst is mixed for approximately15 minutes, filtered and degassed, until all bubbles have disappeared.The compound is then poured over the surface of the matrix 20 which hasbeen treated with the mold release. The glass plate 40 with the appliedprimer layer 42 is placed, primer layer down, on the spacers 36, 38 andimmediately overlies the rubber-catalyst mixture.

A rubber platen 44 is then placed on the glass disc 40, and a mass 46 isplaced on the platen 44 to apply a uniform pressure over the surface ofthe glass 40.

The rubber mixture is then cured. The tempertures and cure times are, ofcourse, related. For lower temperatures, ranging from 160° to 200° F., acuring time of approximately 12 hours can be used. At the higher curingtemperatures, shorter curing times can be used. For example, a 14 milthick, 15 inch diameter mold will cure in approximately 2 hours at 400°F.

At the conclusion of the curing period, the upper plate 40 is separatedfrom the matrix 20. The presence of the mold release on the matrix 20and the primer 42 on the upper glass disc 40 causes the mold thuscreated to adhere to the upper disc 40 and not to the matrix 20.

The completed rubber mold 10, shown in FIG. 3, can then be trimmed tocut away the extruded excess and should be cleaned and vacuumed for usein replication. If the mold release has worked well, the original matrixmay be used to produce yet additional molds. However, because thesurface features on the matrix 20 are merely hardened photoresistmaterial 24 adhering to the glass disc 22, it is not generally expectedthat more than a very limited number of molds can be made from theoriginal matrix 20. A mold 10 once made, however, can be used to casteither replicas, to be used for playback, or submatrices, which may ormay not be used for playback.

Turning next to FIG. 4, the process of producing a replica is partiallyillustrated. In a preferred embodiment, a Mylar polyester film substrate50 is cut into a 15 inch disc and placed on a glass support plate 52.Both are then placed on a turntable 54. The substrate 50 is washed withacetone and Xylene and is spun dry.

A polyurethane resin mixture is then prepared. In the preferredembodiment, a polyurethane resin is employed which is sold by HughsonChemical Company under the designation Chemglaze Z051. Alternatively, asimilar resin, Chemglaze Z052, may also be used. A resin thinner, soldunder the designation Chemglaze 9951 is also used in the preferredembodiment. The resin and thinner are generally used in a ratio of 3parts resin to 2 parts of thinner.

A catalyst sold by the Hughson Chemical Company as Fast Catalyst 9984 or9986 is also employed to speed the polymerization process. In thepreferred embodiment, 10 cc. of catalyst is diluted to 75 cc., using thethinner, prior to use.

Approximately 5 cc. of the diluted catalyst is then mixed with 100 cc.of the diluted resin solution. The combination is mixed well forapproximately 3 minutes and is then "spun" onto the substrate disc 52.With the turntable 54 operating at approximately 400 rpm, a polymer 56coating is spun on for approximately 5 seconds, to result in anapproximately 5 micron layer in the preferred embodiment. The thicknesscan range from 3 to 7 microns.

The methods of applying the coated substrate to the mold 10 are shown inFIG. 5. As shown in FIG. 5A, the preferred technique is to partiallywrap the substrate 50 around a rather large roller 58 and then to rollthe combination onto the mold 10. This method provides a gradualapplication of the resin coated substrate 50 and, at the same time,provides an opportunity to assure an even and uniform application ofpressure to the resin layer 56, while minimizing the occurrence oftrapped bubbles of air or gas in the mold 10.

While the resin layer 56 is setting up, the combination can be rolledagain with a heavier roller. The set-up time runs for from 15 to 45minutes depending upon the resin-catalyst combination and the thicknessof the resin layer 56.

Other materials can be used in addition to the polyurethane resin. Forexample, acrylics and epoxies can also be employed as well as monomerswhich can be polymerized by radiation such as ultraviolet light or radiofrequency energy as taught in the related Broadbent patents, supra.Similarly, substrates other than Mylar polyester film could be employed,including metal foils, which can be thin and flexible.

It has also been found that an alternative casting process can beemployed, as illustrated in FIG. 5B. The resin is thinned and mixed withthe catalyst and applied directly to the mold 10. The substrate 50' isthen rolled onto the resin layer 56' which is then permitted to cure andto adhere the substrate 50' as illustrated in FIG. 6. The finishedreplica will then be substantially the same, no matter which process isemployed.

In FIG. 7, there is shown a method of removing a replica 60 from themold 10. The roller 58 which was used to apply the polymer-substratecombination can be used to remove the cast and cured replica 50. Oneedge of the replica 60 adheres to the roller 58, which, when rotated,removes the cured replica 60 from the mold 10.

Alternatively, an acrylic material may be cast in the mold 10 as shownin FIG. 8. The acrylic replica 62 may be used with a polyester filmsubstrate 63. The acrylic replica can be used interchangeably with thepolyurethane replicas.

It has also been noted that, inasmuch as the acrylic replicas 62 can beplated, the plated acrylic replica 62 can also be utilized as an interimelement in the process of producing stampers for making replicasutilizing embossing techniques.

While the methods of producing the mold and the replicas have beendescribed in terms of a system which utilizes "bumps" to representinformation, it is equally feasible to employ the same process to createa mold whose surface resembles the matrix and from which alternativereplicas can be cast. In the alternative replicas, information isrepresented as depressions in the replica surface.

Similarly, while the present invention has been described in terms of avideo disc system that employs light scattering for the recognition ofinformation, the process steps are equally applicable to phase contrastrecording and playback systems. In such systems, a mold can be createdfrom the original master. The reflecting planes are separated by avertical distance of nλ/4 (where λ is the wavelength of the illuminatingradiation and "n" is an odd integer) and can be easily replicated. Itwould seem that a relatively rigid replica would be preferable for thistype of playback.

Turning finally to FIG. 9, a replica disc 60 is shown in some greaterdetail. The disc 60 includes, in the preferred embodiment, a surfacepattern of discontinuous bumps 64 separated by planar areas 66. Areflective metal coating 68, such as aluminum, is applied by a processsuch as vapor deposition to enhance the reflectivity of the planarportions 66 and to enhance the light scattering capability of theindividual surface deformations 64 representing information.

If desired, an additional, clear plastic coating 70 can be applied tothe disc 60 to protect the metallic surface 68 from scratches, abrasion,and wear. However, with the "non-contact" playback systems, such as aredisclosed in the Elliott patents, supra, as well as the vacuum playbacktransducer and fluid cushion turntables disclosed by Jarsen, supra, thechances of abrasive wear, at least with respect to the playbackmechanism, is minimized.

Thus there has been disclosed a complete process for converting a matrixderived from a master disc into a replica disc for playback. The processincludes, first, a process for creating molds from a matrix. Thereplicas from the first mold could be employed to make additionalsubmolds without any loss is fidelity.

Second, a process is taught for the casting of replicas from the moldsthus taught. The replicas include a surface layer which is apolymerizable compound that has been cast in the mold and a polyestersubstrate, which is bonded to the surface layer to give it structuralintegrity. Additional surface coatings of reflective metal and clearplastic are added to protect the disc from wear and abrasions.

What is claimed as new is:
 1. A mold for use in forming at least theinformation layer of a videodisc, comprising:a rigid plate member; and athin, disc-shaped, elastomeric body on the order of 14 mils thick bondedto a surface of said rigid plate and having an upper surface including aplanar portion and a non-planar portion, said planar portion of saidupper surface being employed for establishing a substantially planarsurface in the resulting molded videodisc suitable for reflecting lightincident thereupon, and said non-planar portion of said upper surfacebeing formed by a plurality of spaced discrete, curvilinear-shaped,discontinuous surface regions extending out of the plane of said planarportion of said first surface, said upper surface carrying informationin the form of a spiral-shaped track having a plurality of individualturns in the spiral, each of said turns being separated from an adjacentone of said turns by a planar portion of said upper surface,saidspiral-shaped track being formed by said curvilinear-shapeddiscontinuous surface regions, said regions being arranged in sequentialorder, and each of said discontinuous surface regions being separatedfrom the next one of said discontinuous surface regions by a planarportion of said upper surface, each of said discontinuous surfaceregions having a constant width in a radial direction on the order of 1micron and a constant maximum dimension in a direction perpendicular tosaid surface on the order of 0.7 microns, the length of eachdiscontinuity in the circumferential direction and the distance betweenadjacent discontinuities in the circumferential direction representingthe stored information.
 2. The mold as claimed in claim 1, wherein saidrigid plate is formed of glass.
 3. An intermediate member for forming atleast the information layer of a videodisc, comprising:a relativelythick and relatively rigid support plate; and a thin, disc-shapedrelatively flexible body approximately 14 mils or less thick bonded to asurface of said rigid plate and having an upper surface including aplanar portion and a non-planar portion, said planar portion of saidupper surface being employed for establishing a substantially planarreflective surface in the resulting videodisc suitable for reflectinglight incident thereupon, and said non-planar portion of said uppersurface being formed by a plurality of spaced discrete,curvilinear-shaped, discontinuous surface regions extending out of theplane of said planar portion of said first surface, said upper surfacecarrying information in the form of a spiral-shaped track having aplurality of individual turns in the spiral, each of said turns beingseparated from an adjacent one of said turns by a planar portion of saidupper surface, said spiral-shaped track being formed by saidcurvilinear-shaped discontinuous surface regions, said regions beingarranged in sequential order, and each of said discontinuous surfaceregions being separated from the next one of said discontinuous surfaceregions by a planar portion of said upper surface, each of saiddiscontinuous surface regions having a constant width in a radialdirection on the order of 1 micron and a constant maximum dimension in adirection perpendicular to said surface on the order of 0.7 microns, thelength of each discontinuity in the circumferential direction and thedistance between adjacent discontinuities in the circumferentialdirection representing the stored information.
 4. The member as claimedin claim 3, wherein said surface discontinuities are generallydepressions in the surface.
 5. The member as claimed in claim 3, whereinsaid surface discontinuities are elevated from the surface.
 6. Themember as claimed in claim 3, wherein said thin body is formed of anelastomeric compound.